Question

The radius and the slant height of a cone are in the ratio 4 : 7. If its curved surface area is 792 $c{m}^2$, find its radius.
$(Use\pi =\frac{22}{7})$

• A. 12 cm
• B. 15 cm
• C. 16 cm
• D. 18 cm

Answer 1

The correct option is A

12 cm

Given, r : l = 4 : 7
If r = 4x, then l = 7x
Curved surface area of cone = 792 $c{m}^2$
$\Rightarrow \pi rl=792\Rightarrow \frac{22}{7}\times 4x\times 7x=792\Rightarrow x^2=\frac{792}{88}=9\Rightarrow x=3cm\therefore Radiusofcone\left(r\right)=4x=4\times 3=12cm$